Multi-pane glass unit having seal with adhesive and hermetic coating layer

ABSTRACT

A vacuum insulated glass unit (VIGU) comprises a first pane of a transparent material and a second pane of a transparent material. The second pane is spaced apart from the first pane to define a cavity therebetween. At least one of a spacer and an array of stand-off members is disposed between the first and second panes to maintain separation therebetween. A first adhesive layer forms at least a portion of a gas-tight connection between the first pane and the second pane. A highly hermetic coating is disposed over the adhesive layer, where the coating is an inorganic layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.S. Provisional Application No.61/350,866, filed on Jun. 2, 2010, and entitled TRANSPARENT FILMS,COATINGS AND LAMINATES FOR VACUUM INSULATING GLASS UNITS (VIGUs) AND FORHIGH-VACUUM INSULATING GLASS UNITS (HVIGUs) (Atty. Dkt. No. STRK-30079).This application also claims benefit of U.S. Provisional Application No.61/422,268, filed on Dec. 13, 2010, and entitled SEAL FOR MULTI-PANEGLASS UNIT HAVING ADHESIVE AND HERMETIC COATING LAYER (Atty. Dkt. No.STRK-30491). In addition, U.S. Pat. No. 7,223,676 is incorporated hereinby reference.

TECHNICAL FIELD

The current disclosure relates to a multi-pane insulating glass unit(IGU) or a multi-pane vacuum insulating glass unit (VIGU) for use infenestration applications (e.g., windows and doors with windows forbuildings); windows for transportation vehicles (e.g., buses, trucks,automobiles, planes, trains, ships); solar collector panels; supermarketrefrigeration systems; beverage vending machine glass units; and suchother applications where an IGU or VIGU might be used. In particular,the disclosure relates to a multi-pane glass unit having a seal withadhesive and hermetic coating layer(s).

BACKGROUND

Insulating glass units (IGUs) are formed by mating at least two panes ofglass to a stand-off system so that at least one cavity is formedbetween the panes, thereby improving the insulating level relative to asingle-pane unit. Vacuum insulated glass units (VIGUs) are a specialtype of IGU where the cavity/cavities between the panes is evacuated,preferably below a pressure of 1 mtorr (i.e., 1 mtorr=1×10⁻³ torr).

IGUs of all types use one or more seals to reduce permeability. Forinsulating glass units (IGUs) that use an internal or external spacer orframe to create the internal cavity, the seals reduce the rate of lossof the fill-gas for gas-filled IGUs and reduce the rate of ingress ofambient air and moisture into the IGU's cavity. For VIGUs, some currentsealing technologies use brittle ceramic bonds such as glass frits.These are costly, require high temperature application, and are prone toreliability failures. By contrast, adhesives allow for low-temperaturebonding with very high glass-to-metal bond strength, and are extremelyinexpensive and also highly reliable. However, the permeability ofconventional adhesives is several orders of magnitude too high tomaintain the high vacuum requirements of VIGUs. A need exists thereforeexists, for a multi-pane glass unit with reliable seals of reducedpermeability.

VIGUs are further challenged in that some glazing materials that areconventionally seen as hermetic, for example, some compositions ofsilica glass, are still sufficiently permeable to gases such as heliumthat the VIGU's internal cavity pressure can rise above 1×10⁻³ torr overthe desired service life of the unit. Other materials, such as metals,can outgas hydrogen at a significant rate, and thereby degrade thequality of the vacuum in the VIGU over its desired service life. A needtherefore exists, for a VIGU comprising materials having improvedhermeticity, so as to better meet the specifications of the windowindustry.

SUMMARY

This disclosure describes multi-pane IGUs and/or VIGUs with coatingsthat significantly decrease the rate of ingress or egress of gases orvapors from the cavity space; and methods for application of suchcoatings.

In one aspect, a vacuum insulated glass unit (VIGU) comprises a firstpane of a transparent material and a second pane of a transparentmaterial. The second pane is spaced apart from the first pane to definea cavity therebetween. At least one of a spacer and an array ofstand-off members is disposed between the first and second panes tomaintain separation therebetween. A first adhesive layer forms at leasta portion of a gas-tight connection between the first pane and thesecond pane. A highly hermetic coating is disposed over the adhesivelayer, where the coating is an inorganic layer.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding, reference is now made to thefollowing description taken in conjunction with the accompanyingDrawings. Note that the dimensions and thicknesses shown are not toscale.

FIG. 1 is an exploded cross-sectional view of a multi-pane glass unit inaccordance with the PRIOR ART, in this case a double-pane IGU;

FIG. 2 is a cross-sectional view of the assembled PRIOR ART IGU of FIG.1;

FIG. 3 a is a cross-sectional view of another multi-pane glass unit inaccordance with the PRIOR ART, in this case a double-pane IGU having a(non-hermetic) secondary sealant applied to the perimeter edges of theIGU;

FIG. 3 b is a perspective cross-sectional view the PRIOR ART IGU of FIG.3 a;

FIG. 3 c is an exploded perspective cross-sectional view of the PRIORART IGU of FIGS. 3 a and 3 b;

FIG. 4 is a cross-sectional view of a multi-pane glass unit inaccordance with one aspect of the invention, in this case a double-paneIGU with a gas-restrictive coating;

FIG. 5 a is a cross-sectional view a multi-pane glass unit in accordancewith another embodiment, in this case a double-pane IGU withgas-restrictive coating and secondary sealant material which covers thegas-restrictive coating;

FIG. 5 b is an exploded perspective cross-sectional view the IGU of FIG.5 a;

FIG. 5 c is a perspective cross-sectional view of the assembled IGU ofFIGS. 5 a and 5 b;

FIG. 6 a is an exploded perspective cross-sectional view of anothermulti-pane glass unit in accordance with an alternative embodiment;

FIG. 6 b is an exploded perspective view of FIG. 6 a.

FIG. 7 is a cross-sectional view of still another multi-pane glass unitin accordance with an alternative embodiment;

FIG. 8 is a cross-sectional view of another multi-pane glass unit inaccordance with the PRIOR ART, in this case a triple-pane IGU;

FIG. 9 shows a cross-sectional view of a multi-pane glass unit inaccordance with another aspect of the invention, in this case atriple-pane IGU with a gas-restrictive coating;

FIG. 10 a shows a cross-sectional view of a triple-pane IGU with agas-restrictive coating and a secondary sealant in accordance with yetanother embodiment;

FIG. 10 b is an exploded perspective cross sectional view of the IGU ofFIG. 10 a;

FIG. 10 c is a perspective cross-sectional view of the assembledtriple-pane IGU of FIGS. 10 a and 10 b;

FIG. 11 shows a cross-sectional view of a suspended-film IGU with agas-restrictive coating in accordance with yet another embodiment;

FIGS. 12 a and 12 b show a perspective cut-away view and a sidecross-sectional view, respectively, of a dual-pane VIGU using a solderglass edge seal and a pump-out tube in accordance with the PRIOR ART;

FIGS. 13 a to 13 c illustrates a method for producing a rigid-edge VIGUin accordance with another aspect of the current invention;

FIGS. 14 a, 14 b and 14 c show cross-sectional views of a multi-paneglass unit (during construction and complete) in accordance with otheraspects of the invention, in this case a double-pane VIGU;

FIGS. 15 a, 15 b and 15 c show cross-sectional views of anothermulti-pane glass unit (during construction and complete) in accordancewith still further aspects of the invention, in this case a double-paneVIGU;

FIGS. 16 a and 16 b show two perspective cross-sectional views of a VIGUcomprising a two-piece flexible metal seal system;

FIGS. 16 c, 16 d, 16 e and 16 f show additional preferred embodiments ofa VIGU in accordance with the invention, and methods of making same;

FIGS. 17 a and 17 b are a perspective cross-sectional view of a VIGUhaving a coating applied onto the inside surfaces of the VIGU, FIG. 17 abeing an assembled view and FIG. 17 b being an exploded view;

FIGS. 18 a and 18 b show a VIGU with at least one pump-out tubeextending through one of the lites to access the window cavity, FIG. 18a being a top view and FIG. 18 b being a cross-sectional side view; and

FIG. 19 is a side view of a glass pane with a scratch or microcrack onthe surface, where the microcrack is filled using the coatingtechnology.

DETAILED DESCRIPTION

Multi-pane insulating glass units or insulating glazing units (IGUs)consist of two or more panes of glass (lites) with a spacer between thepanes around their perimeter, to create a cavity for air or another gas.The number of glass lites is “N” and the number of contained cavities“C” is N−1. (C equals N minus 1.) The number of spacers “S” is N−1. (Sequals N minus 1.) The spacer for a multi-pane IGU (afterwards referredto as simply an IGU) may be held in place with an adhesive or sealant.After assembly of the IGU and the optional filling of the cavity with afill-gas (e.g. argon, krypton or xenon), a secondary seal may be appliedto the perimeter of the glass unit to act as a protective layer againstboth physical damage to the perimeter of the glass unit, as well asproviding additional mechanical strength to the assembly and reducingthe ingress of atmospheric gas into the cavity of the unit or egress(escape) of gas from the cavity of the unit.

For convenience, the following nomenclature is used herein for adual-pane IGU: Lite 1 (“L1”) is the outdoor (i.e., outside-facing) liteand lite 2 (“L2”) is the indoor (i.e., inside-facing) lite; Surface 1(“S1”) is the exterior (i.e., outside-facing) surface on L1, surface 2(“S2”) is the interior (i.e., cavity-facing) surface on L1, surface 3(“S3”) is the exterior (i.e., cavity-facing) surface on L2 and surface 4(“S4”) is the interior (i.e., inside-facing) surface on L2.

Multi-pane vacuum insulating glass units or vacuum insulating glazingunits (VIGUs) are IGUs that have a very low pressure in their cavitiesso as to be more insulating than an air or gas-filled IGUs. The optimalpressure in a cavity of a VIGU is no more than 1×10⁻³ ton, as this isvery close to the point of inflection on the thermal conductivity curvefor low-pressure gases for window geometries. Because no known adhesiveor epoxy is impermeable enough to prevent the ingress of atmosphericgases into the cavity of a VIGU during its life, the two glass panes ofa double-pane VIGU are conventionally sealed using inorganic materials.Current sealing methods for VIGUs include the use of solder glass orglass frit between and at the perimeter of the two lites; metalfoils/ribbons bonded to each of the lites and then welded together tocreate a sealed cavity between the lites; and other hermetic sealingmethods.

The disclosed multi-pane IGUs may have 2, 3, 4 or more glass panes orlites and 1, 2, 3 or more spacer members to create the cavities betweenadjacent pairs of lites. In addition, the disclosed IGUs may incorporatenon-glass panes or barrier films (or “suspended films”) inside the IGUin lieu of one or more internal glass lites. For example, one possiblesuspended film is “Heat Mirror” brand film marketed by SouthwallTechnologies, Inc.

In some embodiments, the disclosed VIGUs may be dual-pane systems havinga basic configuration similar to, e.g., the “SPACIA” brand VIGU marketedby Nippon Sheet Glass Co., Ltd. or the “Pro-VIG” brand VIGU marketed bya German government-sponsored consortium. In other embodiments, thedisclosed VIGUs may be triple pane systems. In still other embodiments,the disclosed VIGUs may be hybrid VIGUs having a basic configurationsimilar to, e.g., the “SPACIA 21” brand VIGU by Nippon Sheet Glass Co.,Ltd. In each case, however, the disclosed embodiments have additionaland/or different structures and/or materials that provide improvedperformance as compared to existing units.

This specification describes multi-pane glass units, whether IGUs orVIGUs, that have one or more surfaces coated in order to reduce the rateof gas permeation into and/or out of the internal cavity/cavities. Insome embodiments, the coatings are applied over glass, to reduce thehelium permeability through glass. In other embodiments, the coatingsare applied over metal, to reduce the rate of out-gassing of hydrogenfrom the metal into the cavity. In still another example, the units aresealed using traditional adhesives, which adhesives are subsequentlytreated with a coating to reduce their permeability. For IGUs, one goalof such a treatment is to reduce the leak rate of the fill-gas (e.g.,argon gas) through the adhesive seal, in order to prolong the lifetimeof the sealed unit. For VIGUs, one goal of such a treatment is toconvert a non-hermetic, adhesive seal into a hermetic one capable ofretaining and maintaining a vacuum in the VIGU cavity over the desiredlife of the window. Means for achieving these improved seals aredescribed herein.

As used herein, the term “adhesive” shall refer to any non-hermeticbonding material, whether a silicone, epoxy, urethane, or any organicsealant.

The present invention disclosed herein comprises, in one aspect thereof,a method for manufacturing an IGU in accordance with traditionalmethods, but further incorporating one or more additional step(s) in themanufacturing process to add a layer of a gas-restricting coating ontothe IGU after it is assembled with at least the primary sealant oradhesive. This coating is done before applying any secondary sealantmember.

This gas-restricting coating layer will significantly reduce the ingressand egress of gases and vapors between the internal cavity of the IGUand the atmosphere outside of, or surrounding the IGU. This will resultin improved IGUs that maintain their insulation properties longerbecause: 1) if the IGUs are filled with a fill-gas (e.g., argon, kryptonor xenon), the improved IGUs will contain the fill-gas at or near theoriginal percentage of fill (i.e., performed in manufacturing) for amuch longer period of time; 2) the gas-restricting coating will reducemoisture penetration or permeation into the cavity of an improved IGU,where such moisture might: a) be visible as a film or condensation onthe internal surfaces of the glass lites, b) be detrimental to coatingsapplied to the internal lite surfaces (e.g., coatings to increase thethermal performance of the IGU), c) increase the corrosion propensity ofthe metallic members of the unit. These same issues apply to IGUs withmore than 2 panes of glass (e.g. triple- and quad-pane IGUs, as well assuspended-film IGUs).

The present invention disclosed herein comprises, in another embodimentthereof, a method for manufacturing an IGU in accordance withtraditional methods, but further adding at least one step in themanufacturing process to add a layer of a gas-restricting coating ontothe IGU after it is assembled with the primary sealant or adhesive butwithout applying the secondary sealant member.

The present invention disclosed herein comprises, in still anotheraspect thereof, a method for manufacturing a multi-pane IGU inaccordance with traditional methods, but further adding at least onestep in the manufacturing process to add a layer of a gas-restrictingcoating onto the IGU after it is assembled with the primary sealant oradhesive and also a secondary sealant member. In this embodiment, thegas-restricting layer may be applied on top of the exposed surfaces of asecondary sealant member. The secondary sealant member may have threeexposed surfaces: 1) the surface in-plane with the IGU's surface S1; 2)the surface perpendicular to the plane of the glass, running from liteL1 to lite L2; and 3) the surface in-plane with the IGU's surface S4.

One or more (exterior) surfaces of the two outside-facing glass lites ofan IGU may be coated with the same gas-restricting coating used to coverthe adhesive or epoxy material during the coating application process.The choice of whether or not a particular embodiment of the processcoats one or both exterior glass surfaces, or uses a mask to selectivelyprevent coating them, or directs the application of the coating onlyonto the desired surfaces of the adhesive or epoxy and other parts ofthe perimeter of the IGU, depends on the beneficial or non-beneficial(undesirable) attributes of the selected gas-restricting coating. Theseattributes include the coating's physical, optical and chemicalproperties. This decision on whether to coat the two exterior-facingglass surfaces applies to dual-pane IGUs as well as to IGUs with morethan two panes of glass (e.g., known in the window industry as triplesor quads), and also to suspended-film IGUs incorporating one or moresuspended film layers and other variations of IGUs.

The present invention disclosed herein comprises, in another aspectthereof, a method of coating the inside of an IGU through the fill-tubesof the IGU. In this method, precursor gases are supplied to the insideof the IGU via the fill tubes, and the precursor gases react inside theIGU to form a gas-restricting coating on the inside of the IGU adhesive.In some embodiments, the IGU adhesive that is coated is apolyisobutylene (PIB, or butyl) material. In other embodiments, adifferent adhesive, for example, a polyurethane material, is used as theprimary adhesive, and this adhesive is subsequently coated with thegas-restricting coating. In some other embodiments, the coating processresults in the formation of inclusions of coating particles inside theadhesive, and these particles are sufficient to restrict gas flow, suchthat a uniform, full coating of the gas-restricting coating over theadhesive is not required.

When the interior surfaces of glass lites comprising an IGU/VIGUinitially have certain low-emissivity (or “low-e”) properties and aresubsequently coated with the gas-restrictive coating material, theinitial low-e properties of the glass may change, depending on thethickness of the gas-restrictive coating. Thus, in some embodiments, theinitial low-e coatings on the glass are selected so that that theyrequire the additional gas-restrictive coating to achieve optimalperformance. Put another way, the emissivity of the glass beforeapplication of the gas-restrictive coating is higher than the emissivityof the glass after application of the gas-restrictive coating.

The present invention comprises, among other things, multi-pane IGUsmanufactured according to any of the above-described methods.

In some embodiments of IGUs, the gas-restricting coating may reduceegress of fill gas from the IGU to <1% of the initial fill-gas volumeper year under severe or extreme use conditions. A plurality ofembodiments are possible depending on the nature of the inert fill-gas.In some embodiments, the fill gas is argon. In some other embodiments,the fill gas is krypton. In still some other embodiments, the fill gasis sulfur hexafluoride.

The conventional method of manufacturing a dual-pane VIGU uses a solderglass (i.e. a glass frit) that bonds the two lites together at theVIGU's perimeter to form a hermetic seal. However, the permeability ofwindow glass or solder glass may be a problem for certain compositionsof glasses. The present invention disclosed herein comprises, in oneaspect, a coating applied over and/or into at least some of the glasscomponents of the VIGU that reduces the permeability of the glass tohelium. In one aspect, the coating is deposited on the glass from thevapor phase. In another aspect, the coating is deposited on the glassfrom the solution phase. In yet another aspect, the coating is createdby diffusing atoms into a thin region near the surface of the glass, sothat the diffusing atoms create a local composition near the surface ofthe glass which is different form the composition in the bulk of theglass, and where this local composition serves to restrict the diffusionof gases such as helium through the glass. In some applications, theglass to be coated is window glass. In some applications, the glass tobe coated is solder glass. In some applications, both window glass andsolder glass are coated.

The present invention disclosed herein comprises, in another aspectthereof, a VIGU comprising a metal component, where the metal componentincludes a coating on at least the cavity-facing side to restrict theoutgassing of hydrogen from the metal into the cavity. The coating onthe metal component may be applied from the vapor phase by methodsincluding, but not limited to, chemical deposition, physical vapordeposition and atomic layer deposition; or it can also be deposited fromthe solution phase by methods including, but not limited to, spraycoating, solvent casting and dip coating.

The present invention disclosed herein comprises, in another aspectthereof, a VIGU with an adhesive as a component, where the adhesive iscoated by a film that impedes gas permeability. In one example, thisVIGU is prepared by first applying an adhesive bond between a lite and asecond surface, and applying a layer of a highly hermetic material tothe perimeter of the VIGUs to cover the outside facing surface of theadhesive or epoxy material (as opposed to the inside or cavity-facingsurface of the adhesive or epoxy material). Advantages of this type ofVIGU may include: a) the ability to hermetically seal the VIGU at lowerprocess temperatures than those required for using a glass frit seal; b)a stronger and/or more flexible seal as compared to a glass frit seal;c) lower cost as compared to a glass frit seal; and d) faster cycle-timeprocess equipment to produce the hermetic seal as compared to a glassfrit seal.

The present invention disclosed herein comprises, in another aspectthereof, a method for manufacturing a hybrid VIGU (e.g., similar to theNSG “SPACIA 21” insulating glass system) of the type that otherwisewould use a conventional hermetic sealant such as a solder glass (i.e.,a glass frit); except in this aspect an adhesive or epoxy would besubstituted for the conventional glass frit, and further the adhesive orepoxy would be subsequently coated with a gas-restricting coating toreduce its permeability to gas. Optionally, in some embodiments anadditional material may be applied to physically protect the perimeteredges of the hybrid VIGU where the secondary sealant layer previouslywould have been used.

The present invention disclosed herein comprises, in another aspectthereof, a VIGU including two thin metal members, one such metal memberattached to each of lites L1 and L2 along the VIGU's perimeter, wherethe metal members are bonded to the glass using an adhesive or epoxy.This aspect also includes a method of bonding the metal to the glassusing adhesive, and subsequently joining together the two metal piecesusing a metal joining process (e.g., welding) to create a sealed VIGU(not including any temporary gas evacuation port), where the adhesive orepoxy is coated with a highly hermetic material layer after the bondingstep. In one embodiment, the adhesive or epoxy used to create theglass-to-metal bonds that will be outside the VIGU's low-pressure (i.e.,high-vacuum) cavity remains uncoated so that the adhesive or epoxybonding material can out-gas or otherwise exchange gases and achieveequilibrium with the atmosphere surrounding the outside of the VIGU. Inanother embodiment, the adhesive forms a fillet on the outside-facingsurface, and in some preferred embodiments this fillet is purposefullyabraded to remove the hermetic coating, allowing equilibrium between theadhesive and the environment. In another embodiment, a fillet is left onthe outside of the cavity but not on the inside, and the hermetic layeron the fillet will crack on the fillet side but not the cavity sideduring thermal cycling because of larger stresses on the fillet surface,restoring said equilibrium during normal use. In another embodiment, theVIGU has more than two glass panes, and more than one contained cavityfor the low-pressure (i.e., high-vacuum) environment.

The glass lites of a VIGU could be coated with the same highly hermeticcoating used to cover the adhesive or epoxy material during the samehermetic coating application process. As described above for an IGU, ifdesired, these glass surfaces may be selectively masked to preventcoating of some or all of the glass surfaces.

In embodiments where the surfaces of the glass lites are coated with thehighly hermetic material, the low-e properties of the glass may changesignificantly. Thus, in some embodiments, the low-e coatings on theglass are selected such that that they require the highly hermeticcoating to achieve optimal performance: e.g., the emissivity of theglass before application of the highly hermetic coating is higher thanthe emissivity of the glass after application of the highly hermeticcoating.

The present invention disclosed herein comprises, in another aspectthereof, a VIGU that is sealed with adhesive, where the VIGU's interiorcompartment is in fluid communication with the exterior via one or more(temporary) gas access ports. The present invention discloses herein amethod for coating the inside of the VIGU with a highly hermeticmaterial using gas phase precursors that access the interior via thesegas access ports. In this method, the VIGU is evacuated through theseport(s) after the coating process is complete, and the port(s) aresealed shut. Thus, the entire coating process is confined to theinterior of the VIGU.

The present invention disclosed herein comprises, in another aspectthereof, a method for manufacturing a VIGU which uses a thin metal sealattached to lites L1 and L2 to create the hermetic seal at the VIGU'sperimeter, where the bond between the glass and metal is coated orinfused with a chemical or material that restricts gas transport. One ormore bonding methods including, but not limited to, ultrasonic bonding,diffusion or thermal-compression bonding, chemical bonding with orwithout mechanical assistance, and glass-frit bonding, may be used tobond the glass to the metal. After the metal members are joined togetherto create a sealed VIGU, the glass-to-metal bond is coated on itsinternal and/or external surfaces with a highly hermetic material layer.In the absence of the highly hermetic coating, defects and/or damage(e.g., cracking) that may occur during the manufacturing process orsubsequently may allow gas permeation through the seal even though suchdefects do not mechanically degrade or separate the glass-to-metal bond.The highly hermetic coating applied in accordance with this aspectbridges and strengthens the defects and/or damage to prevent permeationof any gases into the evacuated cavity, and to inhibit further crackgrowth. In this embodiment, it is possible to coat locally, just thebonded region, although a method which coats the entire assembly is alsoenvisioned.

In some embodiments, a highly hermetic coating is applied over theinterior glass of a VIGU that fills microcracks on the glass surface,and thus improves the resistance of the glass to fracturing understress. In this embodiment, the 1-sigma or 2-sigma or 3-sigma or 4-sigmaor 5-sigma or 6-sigma (i.e., where each sigma=one standard deviationfrom the mean) minimum compressive stress needed to fracture the glasswhen applied by a 0.2 to 1 mm diameter stainless steel cylinder isimproved by the coating process. This coating may be applied at anypoint during the assembly process, for example, before and/or after theglass is bonded to a metal member, or before and/or after the lites arejoined to form an internal cavity. In one example, this coating isaluminum oxide deposited by atomic layer deposition.

In some examples, the gas-restrictive coating material described for theIGU is different from the highly hermetic coating material of the VIGU.In other embodiments, the gas-restrictive coating material for the IGUis the same as the highly hermetic coating material of the VIGU.

Referring now to FIG. 1, there is shown an exploded cross-sectional viewof a multi-pane glass unit (in this case a double-pane IGU) inaccordance with the PRIOR ART. The IGU 100 comprises a first lite 101and a second lite 102. A spacer 106 is attached to lites 101 and 102with an adhesive or epoxy material 104. The adhesive or epoxy material104 bonds the spacer 106 to the inside surface of lite 101. If lite 101is configured in the window assembly as the outdoor-facing lite (denotedL1), then the lite's top surface or outdoor-facing surface is referredto by the window industry as surface 1 (denoted S1). The oppositesurface, which is attached to spacer 106 by the adhesive or epoxymaterial 104, is referred to as surface 2 (denoted S2). The spacer 106is attached to lite 102 (denoted L2) using adhesive or epoxy material105. In many common uses, the adhesive is butyl, but other materials mayalso be employed. Hereafter, “adhesive or epoxy material” will bereferred to as “adhesive”, “an adhesive” or “the adhesive”. The surfaceof lite 102 in contact with adhesive 105 is referred to by windowindustry as surface 3 (denoted S3). The opposite surface of lite 102,which in this example would be facing the indoor side of a wall, isreferred to by the window industry as surface 4 (denoted S4).

Referring now to FIG. 2, there is shown a cross-sectional view theassembled PRIOR ART IGU 100 whose components were defined in thedescription of FIG. 1. The adhesive 104 is used to attach lite 101 tospacer 106. Spacer 106 is attached to lite 102 using the adhesivematerial 105. The assembled unit creates a cavity, 112, in between thetwo lites.

Referring now to FIG. 3 a, there is shown a cross-sectional view of analternative IGU in accordance with the PRIOR ART. IGU 300 is similar tothat described in FIGS. 1 and 2, but further comprising a secondary seal(or secondary sealant) 307. This secondary seal 307 is applied to theperimeter edges of the IGU 300 to provide physical protection, to act asa barrier to reduce the rate of ingress of outside air and moisture intothe IGU's cavity 112 and/or to reduce the rate of egress (rate ofescape) of any fill-gas inserted into the cavity 112 as part of theIGU's assembly process.

Referring now to FIG. 3 b, there is shown a perspective cross-sectionalview of the PRIOR ART IGU 300 of FIG. 3 a, including the lites 101 and102, spacer 106 and secondary sealant 307 applied to the perimeter edgesof the IGU.

Referring now to FIG. 3 c, there is shown an exploded, perspectivecross-sectional view of the PRIOR ART IGU 300 of FIGS. 3 a and 3 b.

Referring now to FIG. 4, there is shown a cross-sectional view of amulti-pane glass unit in accordance with one embodiment, in this case adouble-pane IGU. IGU 400 comprises a first lite 401 (L1), a firstadhesive layer 404, a spacer 406, a second adhesive layer 405, a secondlite 402 (L2) and an internal cavity 412. In some embodiments, aplurality of stand-off members (not shown) may be provided in theinternal cavity to maintain separation of the lites. In this embodiment,a gas-restrictive coating material 408 is disposed along the perimeteredge of the IGU. This gas-restrictive material 408 is applied as part ofthe IGU's assembly process to the perimeter edge of the IGU, serving asa barrier to reduce the rate of ingress of outside air and moisture intothe IGU's cavity 412, and further to reduce the rate of egress (i.e.,rate of escape) of any fill-gas inserted into the cavity 412 to a muchgreat extent than conventional secondary sealant material is capable ofdoing. In this embodiment, there may be no secondary sealant.

Referring now to FIG. 5 a, there is shown a cross-sectional view amulti-pane glass unit in accordance with another embodiment of thecurrent invention, in this case a double-pane IGU with secondarysealant. IGU 500 comprises a first lite 501 (L1), a first adhesive 504,a spacer 506, a second adhesive 505 and a second lite 502 (L2), togetherdefining an interior cavity 510. In some embodiments, a plurality ofstand-off members (not shown) may be provided in the internal cavity tomaintain separation of the lites. A gas-restrictive coating material 508is disposed along the perimeter edge of the IGU 500, and the coatingmaterial is overlaid by a secondary seal or secondary sealant material507. The secondary seal 507 protects the gas-restrictive material 508against physical damage. If a fill-gas is used in cavity 512, thecoating layer 508 and the secondary sealant 507 may be applied beforeand/or after the gas fill procedure is performed. Otherwise, thepump-out opening (best seen in FIGS. 17 a and 17 b) used to fill thecavity 512 would have to be sealed after coating layers 508 and then 507are applied and after completion of the gas-fill operation.

Referring now to FIG. 5 b, there is shown an exploded, perspectivecross-sectional view of the IGU 500. The gas-restrictive coatingmaterial 508 is clearly shown blocking all ingress and egress of gasto/from the cavity 512 through the adhesives 504 and 505 and/or spacer506.

Referring now to FIG. 5 c, there is shown a perspective cross-sectionalview of the assembled IGU 500 of FIGS. 5 a and 5 b.

Referring now to FIG. 6 a, there is shown a perspective cross-sectionalview of a multi-pane glass unit in accordance with another embodiment,in this case a double-pane IGU similar in most respects to IGU 500. TheIGU 600 comprises a first lite 601 (L1), a first adhesive 604, a spacer606, a second adhesive 605 and a second lite 602 (L2), together definingan interior cavity 612. In some embodiments, a plurality of stand-offmembers (not shown) may be provided in the internal cavity to maintainseparation of the lites. A gas-restrictive coating material 608 isdisposed along the perimeter edge of the IGU 600, and the coatingmaterial is overlaid by a secondary seal or secondary sealant material607. The secondary seal 607 protects the gas-restrictive material 608against physical damage. In this embodiment, however, the spacer 606,primary sealant/adhesive 604, 605 bonding the spacer 606 to lites 601,602, the highly hermetic (i.e., gas-restrictive) coating 608 and thesecondary seal 607 are recessed inwards toward the center of the IGU(i.e., disposed substantially between the lites 601, 602). This avoidshaving the secondary sealant 607 protrude past the perimeter edges oflites 601 and 602.

Referring now to FIG. 6 b, there is shown an exploded perspectivecross-sectional view of a cross-section of the assembled IGU 600 of FIG.6 a. This view clearly shows that the gas-restrictive coating material608 is configured to completely block gas ingress and egress to/from thecavity 612 even when the seal 606 and adhesives 604, 605 are insetbetween the lites 601, 602.

Referring now to FIG. 7, there is shown a multi-pane glass unit inaccordance with still another embodiment of the current invention, inthis case a double-pane IGU. IGU 700 comprises a first lite 701, a firstadhesive 704, a spacer 706, a second adhesive 705 and a second lite 702,collectively defining an interior cavity 712. In some embodiments, aplurality of stand-off members (not shown) may be provided in theinternal cavity to maintain separation of the lites. In this embodiment,a secondary sealant 707 is disposed around the perimeter of the IGU(i.e., directly over the sides of the lites, spacer and adhesives) and agas-restrictive material 708 is then disposed over the remaining exposedsurfaces of the secondary sealant.

Referring now to FIG. 8, there is shown a cross-sectional view of amulti-pane glass unit in accordance with the PRIOR ART, in this case atriple-pane or “triple” IGU. A triple IGU is sometimes used instead of adual-pane or double-pane IGU (FIGS. 1 through 3 c), most often toachieve higher insulating properties than a typical dual-pane IGU canachieve. The triple-pane IGU 800 has two insulating cavities 812 and 813instead of the single cavity of a dual-pane IGU. A triple-pane IGU isusually more insulating than a double-pane IGU because a triple has twoinsulating cavities for containing air or a fill-gas compared to onecavity in a double-pane IGU. In this example, a first adhesive 804 isused to attach a first lite 801 to a first spacer 806. First spacer 806is attached to a second lite 802 using a second adhesive material 805.The second lite 802 is attached to a second spacer 810 using a thirdadhesive 809, and the second spacer 810 is attached to a third lite 803using a fourth adhesive 811.

Referring now to FIG. 9, there is shown a cross-sectional view anassembled multi-pane glass unit in accordance with another embodiment ofthe current invention, in this case a triple-pane IGU. The triple-paneIGU 900 comprises a first lite 901 attached with a first adhesive 904 toa first spacer 906. The first spacer 906 is attached to a second lite902 using a second adhesive material 905. The second lite 902 isattached to a second spacer 910 using a third adhesive 909, and thesecond spacer is attached to a third lite 903 using a fourth adhesive911. The previously described elements of IGU 900 define two insulatingcavities 912 and 913 between the lites 901, 902 and 903. In someembodiments, a plurality of stand-off members (not shown) may beprovided in the internal cavities to maintain separation of the lites.IGU 900 further comprises a gas-restrictive coating layer 908 disposedover the sides of the lites 901, 902 and 903, spacers 906 and 910 andadhesives 905, 905, 909 and 911 along on the side of the triple IGU.

Referring now to FIG. 10 a, there is shown a cross-sectional view of atriple-pane IGU in accordance with a preferred embodiment of the currentinvention. FIG. 10 a, in conjunction with FIGS. 10 b and 10 c, alsoillustrates a preferred method for using a gas-restrictive coating layer1008 on a triple IGU. IGU 1000 comprises a first spacer 1006 is attachedto a first lite 1001 using a first adhesive material 1004. The firstspacer 1006 is attached to a second lite 1002 using a second adhesivematerial 1005. The second lite 1002 is attached to a second spacer 1010using a third adhesive 1009, and the second spacer is also attached to athird lite 1003 using a fourth adhesive 1011. The previously describedelements of IGU 1000 define two insulating cavities 1012 and 1013between the lites 1001, 1002 and 1003. In some embodiments, a pluralityof stand-off members (not shown) may be provided in the internalcavities to maintain separation of the lites. A gas-restrictive coatinglayer 1008 is applied to the perimeter edges of the lites 1001, 1002 and1003, spacers 1006 and 1010 and adhesives 1005, 1005, 1009 and 1011 ofthe assembled IGU 1000. A secondary sealant 1007 may be applied over thegas-restrictive coating layer 1008 to protect it from physical damage.If a fill-gas is used in cavities 1012 and 1013, the coating layer 1008may be applied before or after the gas fill procedure is performed.

Referring now to FIG. 10 b, there is shown an exploded perspectivecross-sectional view the IGU 1000 of FIG. 10 a.

Referring now to FIG. 10 c, there is shown a perspective cross-sectionalview of the assembled IGU 1000 of FIGS. 10 a and 10 b.

Referring now to FIG. 11, there is shown a cross-sectional view of asuspended-film IGU in accordance with a yet another embodiment. Theconstruction of IGU 1100 is similar in most respects to IGU 1000 ofFIGS. 10 a, 10 b and 10 c, except that the glass second lite is replacedwith a suspended film 1114. The suspended film 1114 may be formed of aplastic, polymer or other material known for use as suspended films. Thesuspended film 1114, along with the other components, defines insulatingcavities 1012 and 1013. Optionally, a secondary sealant material (notshown) may be used to cover the perimeter edges of the suspended filmIGU 1100. A desiccant material 1115 may be provided in the interior ofthe first spacer 1006 and/or in the interior of the second spacer 1010.

Referring now to FIGS. 12 a and 12 b, there is shown a perspectivecut-away view (FIG. 12 a) and a side cross-sectional view (FIG. 12 b) ofa dual-pane VIGU in accordance with the PRIOR ART. The VIGU 1200comprises a first lite 1201 and a second lite 1202 spaced apart by aplurality of support pillars 1203 to define a cavity 1204 therebetween.An edge seal 1206 formed of solder glass is provided around theperiphery of the lites 1201 and 1202 to isolate the cavity 1204. Apump-out tube 1205 is provided on one of the lites for evacuating thecavity 1204 after the assembly of the VIGU. The pump-out tube 1205 mayalso have a solder-glass edge seal 1207. This type of VIGU (similar tothe “SPACIA” brand by NSG) is considered to have a “rigid edge seal” dueto the low or non-flexibility of the solder-glass seal system.

Referring now to FIGS. 13 a to 13 c, there is illustrated a method forproducing a rigid-edge VIGU in accordance with another aspect of thecurrent invention. As seen in FIG. 13 a, a VIGU 1300 comprises a firstlite 1301, a second lite 1302 spaced apart from the first lite, and aplurality of stand-offs 1303 that maintain the separation between thelites to form an internal cavity 1304 therebetween. As seen in FIG. 13b, a solder glass seal 1317 is made inside the perimeter (i.e., thelateral boundaries) of the VIGU 1300. As seen in FIG. 13 c, a highlyhermetic coating 1318 is applied to the outside-facing fillet of thesolder glass (the side opposite the VIGU's internal cavity 1304). Apump-out tube (not shown) may be provided to allow evacuation of theinternal cavity 1304.

Referring now to FIGS. 14 a, 14 b and 14 c, there is shown across-sectional view of a multi-pane glass unit in accordance withanother aspect of the invention, in this case a double-pane VIGU. Amethod of producing the VIGU is also illustrated. The VIGU 1400comprises a first lite 1401 and a second lite 1402 spaced apart by aplurality of support pillars 1417 (FIG. 14 c) to define a cavity 1410therebetween (FIG. 14 c). A pump-out tube (not shown) may be provided onone of the lites for evacuating the cavity 1410 after the assembly ofthe VIGU 1400. As best seen in FIG. 14 a, a first metal-foil frame 1405is attached to the inner surface (S2) of the first lite 1401 using afirst adhesive 1403 and a second metal-foil frame 1409 is attached tothe inner surface (S3) of the second lite 1402 using a second adhesive1404. As seen in FIG. 14 b, after adhesive bonding, the exposed portionsof the adhesives 1403 and 1404 on what will become the adhesive'scavity-facing surface (i.e., cavity 1410) are subsequently coating withthe highly hermetic material 1407. In the VIGU 1400, the coating 1407 isdirected just over the area of the adhesive, and the rest of the windowand metal are uncoated (e.g., through the use of directional applicationof the coating, or through masking). Subsequently, the stand-offs 1507for maintaining mechanical separation of the lites are placed on orattached to surfaces S2 and/or S3, and the lites 1401 and 1402 arebrought into contact with the stand-offs. As seen in FIG. 14 c, theoutside perimeters of the two metal-foil frames 1405 and 1409 may thenbe welded together (or joined with another known hermetic metal joiningprocess) to complete the hermetic seal. Evacuation of the cavity 1410may be accomplished by use of the pump-out tube (if provided), oralternatively, by performing the final weld with the VIGU assemblylocated in an evacuated (i.e., vacuum) chamber.

Referring now to FIGS. 15 a, 15 b and 15 c, there is shown across-sectional view of a multi-pane glass unit in accordance with yetanother aspect of the invention, in this case an alternative double-paneVIGU. A method of producing the VIGU is also illustrated. The VIGU 1500is similar in most respects to that of FIGS. 14 a, 14 b and 14 c,comprising a first lite 1501 and a second lite 1502 spaced apart by aplurality of stand-off members (support pillars) 1517 (FIG. 15 c) todefine a cavity 1510 therebetween. A pump-out tube (not shown) may beprovided on one of the lites for evacuating the cavity 1510 after theassembly of the VIGU 1500. As best seen in FIG. 15 a, a first metal-foilframe 1505 is attached to the inner surface of the first lite 1501 usinga first adhesive 1503 and a second metal-foil frame 1509 is attached tothe inner surface of the second lite 1502 using a second adhesive 1504.After adhesive bonding, the exposed portions of the adhesives 1503 and1504 on what will become the adhesive's cavity-facing surface aresubsequently coating with the highly hermetic material 1507. As bestseen in FIG. 15 b, in the VIGU 1500, all of the cavity-facing surfaces(i.e., adhesive, metal, and glass) are coated with the coating 1507. Instill another embodiment (not shown) both the cavity-facing andoutside-facing surfaces may be coated. Subsequently, the stand-offs 1507are placed on or attached to the inner surfaces of the lites 1501 and/or1502, and both lites are then brought into contact with the stand-offs.As seen in FIG. 15 c, the outside perimeters of the two metal-foilframes 1505 and 1509 may then be welded together (or otherwisehermetically joined) to complete the hermetic seal. Evacuation of thecavity 1510 may be accomplished by use of the pump-out tube (ifprovided), or alternatively, by performing the final weld with the VIGUassembly located in an evacuated (i.e., vacuum) chamber.

Referring now to FIGS. 16 a and 16 b, there are illustrated twoperspective cross-sectional views of a VIGU 1600 comprising a two-pieceflexible metal seal system made of first and second pre-formed metalpieces 1622 and 1623 (sometimes referred to as a bellows) for creating ahermetic seal between a first lite 1601 and a second lite 1602. Thelites 1601 and 1602 are spaced apart to form a cavity 1610 therebetween.As best seen in FIG. 16 a, the first metal bellows piece 1622 may bebonded directly to the first glass lite 1601 at the first glass-to-metalbond region 1626, and the second metal bellows piece 1623 may be bondeddirectly to the second glass lite 1602 at the second glass-to-metal bondregion 1628. As best seen in FIG. 16 b, the first metal bellows piece1622 has a cavity-facing seal exposure 1629 on bond region 1626 and anambient atmosphere seal exposure 1630 on bond region 1626. Similarly,the second metal bellows piece 1623 has a cavity-facing seal exposure1631 on bond region 1628 and an ambient atmosphere seal exposure 1632 onbond region 1628. After assembly of this VIGU 1600, including theplacement of a stand-off system (not shown) between lites 1601 and 1602to prevent the two lites from coming into contact with each other, theVIGU 1600 is sealed shut in a vacuum by welding the two bellows togetherat their perimeters 1638. Alternatively, the cavity 1610 may beevacuated by the use of a pump-out tube (not shown). There are severalknown methods for producing hermetic glass-to-metal bonds, including butnot limited to soldering the metal to a pre-metalized surface of theglass with a metal alloy solder; using a glass frit material (a solderglass) to solder the metal to the glass surface; diffusion bonding theglass to the metal; and chemically bonding the glass to the metal usinga catalyst to assist with some form of mechanical agitation such asultrasonic bonding.

Referring now to FIGS. 16 c, 16 d, 16 e and 16 f, there are illustratedadditional preferred embodiments of a VIGU in accordance with theinvention, and methods of making same. Similar in many respects to theembodiments of FIGS. 16 a and 16 b, in these embodiments a two-pieceflexible metal seal system comprising preformed metal members(“bellows”) 1622 and 1623 is used to create the hermetic seal betweenlites 1601 and 1602. As seen in FIG. 16 c, a first metal bellows member1622 is bonded with an adhesive 1620 to a first lite 1601. A secondmetal bellows member 1623 is bonded with an adhesive 1621 to a secondlite 1602. Subsequent to the adhesive glass-to-metal bonding process, atleast some of the exposed surfaces of adhesives 1620 and 1621 (i.e., thesurfaces that will later be exposed to the cavity 1610 containing thehigh vacuum) are covered with a highly hermetic coating 1625. As shownin FIG. 16 d, the adhesive 1620 may be coated with gas-restrictivecoating material 1625 a and the adhesive 1621 may be coated agas-restrictive coating 1625 b (which may be the same material as 1625a). In some embodiments (e.g., FIG. 16 d), only the cavity-facingsurfaces of the adhesive 1620 and 1621 are coated with thehighly-hermetic layers 1625 a and 1625 b. In other embodiments (e.g.,FIG. 16 e), the VIGU's outside-facing glass surfaces S1 (of lite 1601)and S4 (of lite 1602) may be coated with a highly-hermetic materiallayer 1625 c on surface S1 and 1625 d on surface S4. This secondapproach does not require directing the coating only onto the exposedadhesive surfaces or masking the glass during the coating applicationprocesses.

As seen in FIG. 16 f, after coating with the highly hermetic,gas-restricting coating 1625, the lites 1601 and 1602 are brought intoproximity with one another; separation between the lites beingmaintained by a plurality of stand-off members 1618. Next, the metalseal members 1622 and 1623 are shaped into the required form (e.g.,bellows-shaped) if not already so configured, and moved into contactwith one another. Finally, the metal seal members 1622 and 1623 arewelded or otherwise hermetically joined to form a junction 1616, therebycreating a hermetic cavity 1610 between the lites 1601 and 1602, as wellas within the bounds of the seals. The gas-restricting coatings 1625 arenot shown in FIG. 16 f, but are understood to be present on the areas1625 a and 1625 b indicated in FIG. 16 d and/or the areas 1625 c and1625 d indicated in FIG. 16 e.

Referring now to FIG. 17 a, there is shown a perspective cross-sectionalview of a multi-pane glass unit in accordance with another embodiment,in this case a VIGU. The VIGU 1700 is similar to those previouslydescribed herein, comprising a first lite 1701, a first adhesive 1704, aspacer 1706, a second adhesive 1705 and a second lite 1702, togetherdefining an interior cavity 1712. A highly hermetic coating material1708 is disposed onto the inside surfaces (e.g., glass, metal andadhesive) defining cavity 1712 through fill-tubes 1736 and 1737. Thiscoating may be in lieu of coating the exterior perimeter or all exteriorsurfaces of an assembled IGU with or without a secondary seal.Typically, one or more of the holes 1736 and 1737 shown for the filltubes would be located at the top side of the spacer unit. In thisperspective cut-away view, the holes are shown on a side and bottomlocation for clarity. Coating the interior surfaces of the cavity 1712may be an advantage because only the cavity-facing surfaces of theprimary adhesives (sealants) 1704 and 1705 are coated rather than theirexterior-facing surfaces. Since these sealants will outgas somematerials over time, any materials outgassed from the sealants wouldmostly go into the atmosphere or into and eventually through thesecondary sealant 1707 (if provided) instead of into the cavity 1712. Ifthe coating 1708 is highly-hermetic and not just a gaspermeation-reducing material, even less undesirable outgassed materialswill enter into the cavity 1712.

Referring now to FIG. 17 b, there is shown an exploded perspectivecross-sectional view of the VIGU 1700 of FIG. 17 a. It will beappreciated that in FIG. 17 b the highly hermetic coating 1708 isillustrated in a three-dimensional, free-standing form to show thecontours of the coating after application, however, it will beunderstood that the coating is typically applied in-situ and cannot beremoved as shown.

Referring now to FIGS. 18 a and 18 b, there is shown a VIGU 1800 with atleast one pump-out tube 1836. The VIGU 1800 comprises a first lite 1801,a plurality of stand-off members 1818, a second lite 1802, and sealmembers 1819, these components together defining a sealed interiorcavity 1812. The pump-out tube 1836 passes from the exterior of thecavity 1812 into the interior, typically passing through one of thelites 1801 and 1802. In some constructions of a VIGU 1800, the VIGU isassembled and sealed under atmospheric conditions, and the gas in cavity1812 is evacuated through the tube 1836. In this aspect of theinvention, the pump-out tube is used to feed in precursor gases thatreact on the cavity-facing surfaces to form a highly hermetic coating1825 (not shown) on the inside surfaces of the cavity 1812. Theprecursor gases are subsequently evacuated from the cavity 1812 and thetube 1836 is sealed to hold the vacuum.

Referring now to FIG. 19, there is shown a cross sectional view of aglass lite 1901 with a scratch (or microcrack) 1938 on its surface. Thecoating process is applied to the surface, and the coating 1925 fillsthe microcrack and mechanically stabilizes it against fracture.

Table 1 provides a list of materials currently believed suitable for useas the gas-restricting coating, also referred to as the highly hermeticcoating, described in connection with the aspects and embodimentsdisclosed herein.

TABLE 1 Potential materials for use as the highly hermetic coating formulti-pane IGUs and VIGUs. Nitrides: AlN, TaNx, NbN, TiNx, BN, MoN, WxN,ZrN, HfN, GaN, InN Carbides: TiC, NbC, TaC Elements: Pt, Ru, Ir, Pd, Rh,Cu, Fe, Mo, Co, Ni, W, Cu, Ag Sulfides: ZnS, SrS, CaS, PbS Fluorides:CaF2, SrF2, ZnF2, MgF2, LaF3 Oxides: Al2O3, TiO2, Ta2O5, Nb2O5, HfO2,ZrO2, SiO2, ZnO, MgO, La2O3, Y2O3, Sc2O3, Er2O3, V2O5, CeO2, SnO MetalInGa, SnAu Alloys:

Several different coating processes can be used to prepare agas-restrictive or highly hermetic seal for an IGU or VIGU, includingbut not limited to: sol-gel; electroless deposition; chemical vapordeposition; physical vapor deposition; and atomic layer deposition.Examples of each coating method are described below.

The methods of coating of VIGUs are very similar that for coating IGUs,with the difference being largely related to performance: A VIGU mustmaintain a pressure of less than 1 millitorr (1×10⁻³ torr) over itsdesired 10-40 year life in order to maintain its low U value. As aresult, the VIGU coatings herein are referred to as “highly hermetic”.For IGUs, the goal of a gas restrictive coating is to keep the leak rateof argon down to less than 1% of the cavity volume per year, so that nothermally significant change in gas composition will occur over thelifetime of the system; these coatings are referred to as “gasrestrictive”. For VIGUs, the most significant gas is helium, which ispresent in the atmosphere at 5 ppm, and has by far the highest diffusionmobility of any atmospheric gas. The leak rate of helium through thebond line produced by the highly hermetic coatings of this inventionshould ideally be less than 1×10⁻⁸ cc(STP)/sec, and even more preferredto be less than 1×10⁻¹⁰ cc(STP)/sec (where STP is Standard Temperatureand Pressure) for a 1 m² meter window. Clearly, a “highly hermetic”coating will also function to be “gas restrictive”, but the converse isnot necessarily true. The two types of coatings may be made of exactlythe same material, or by similar processes, or with entirely differentmaterials and processes, as long as the cost and performancespecifications for the application are met.

The gas-restrictive coating may be added to the surface of the primarysealant, but before the application of the secondary sealant. This maybe accomplished, for example, by applying a sol-gel precursor in waterto the surface of the primary sealant, where the sol-gel precursor curesor matures into a dense, thin ceramic film after the evaporation ofwater. In this application, it may be preferred to oxidize the exteriorsurface of the primary sealant, in order to improve its wettability.This may be accomplished by, for example, exposing the exterior of theprimary sealant to a corona discharge or downstream plasma, in order tooxidize the surface of the sealant. Examples of materials that aredeposited using sol-gel techniques include silica and titania. In someembodiments, after the coating process, the window is heated toapproximately 60° C. to further cure the sol-gel material.

In another aspect of this invention, application of a coating may beaccomplished by electroless deposition of a metal such as copper,nickel, silver, or tin-gold eutectic, to form a microns-thin metal layeron the sealant. For this approach, one can use a commercially availableelectroless metal solution such as the “Enshield Plus” brand nickelsystem available from Enthone, Inc. In this solution it is not requiredthat the deposited material be pure; large percentages of impurities(such as those commonly seen in high phosphorous nickel coatings) areexplicitly envisioned. Regardless of what solution is used, electrolessdeposition typically occurs through the steps of: 1) cleaning thesubstrate to remove oils and debris; 2) activating the substrate throughproprietary chemistries, commonly a tin reagent; 3) deposition of apalladium seed layer on the activated surface; and 4) electroless metaldeposition atop the seed. Typical electroless processes deposit filmsfrom 0.01 μm to 10 μm, thicknesses which are acceptable for thisapplication. In a preferred embodiment, the thickness of the electrolesslayer is from 0.1 to 10 μm; in a more preferred embodiment, it is from0.5 to 2 μm.

In another aspect of this invention, the coating is applied by very lowtemperature chemical vapor deposition, such as that described in U.S.Pat. No. 7,223,676, which is incorporated herein by reference. In oneexample of such a process, the window is placed into a chambercontaining a silicon-containing gas such as silane, and molecularoxygen, and a torroidal plasma is ignited to deposit the vapor phasematerial onto the window.

In another aspect of this invention, the coating is applied by aphysical vapor deposition process such as sputtering. In one example,the glass of the window is masked by an adhesive polymer film, andoriented to expose part of the adhesive bond to the sputter source, andthe sputtering process is performed. The window is then rotated toexpose a second part of the adhesive bond to the sputter source, andthis process is repeated as needed to coat the adhesive seal.

In a preferred embodiment of this invention, a gas-restrictive coatingis created by an atomic layer deposition (ALD) process. In ALD, thesubstrate is exposed sequentially to two precursor compounds, which eachattach to the exposed substrate surface. The deposition is repeated overmultiple cycles, where each cycle results in growth of the coating by asingle atomic layer. A preferred coating material is alumina, which isformed from the two precursors trimethylaluminum and water, where atypical temperature of deposition ranges from 25° C. to 80° C.

ALD is a conformal coating technique, where the precursors coat allexposed surfaces equally, whether or not they are in the line-of-sight.For ideal ALD processes, it is critical to remove the first precursorcompletely from the gas around the surface before introducing the secondprecursor. Failure to do so will result in gas-phase reaction betweenthe two precursors, and a “pseudo-CVD” deposition where the uniformityof the coating is not perfect over all parts of the geometry. For thisinvention, true ALD is not absolutely required, and pseudo-CVD candeliver appropriate coverage as long as the non-uniformities are not toosevere. Pseudo-CVD also has the advantage that less time is required topurge the system between precursors. However, for the remainder of thisspecification, the phrase “ALD” is meant to encompass both true ALD andpseudo-CVD depositions processes unless otherwise noted.

The thickness of an ALD coating on adhesives can be difficult to definefor small thicknesses, because the ALD film will nucleate inside theadhesive in the first layers, before forming a coating on top of it.Different adhesives will require different number of cycles before thesenuclei coalesce to form a uniform coat. Therefore, to accommodate suchdifferences, all of the thicknesses below represent thicknesses achievedby an equivalent number of deposition cycles on glass, and the thicknessof the inorganic coating over an adhesive is expected to be slightlyless. Alternatively, the ALD coating can be specified by the number ofcycles applied, and in some cases below an estimate of number of cyclesneeded to produce a given thickness coating is also provided.

An ALD-based gas-restrictive coating is most easily deposited by placingan IGU that has been sealed by an adhesive into an ALD chamber, anddepositing alumina to a thickness of about 0.4 nm to 1 μm. A preferredrange of thickness is from 1-60 nm for effective barrier properties atminimal cycle time, which corresponds to roughly 12 to 800 cycles ofALD; thinner films will also work for this gas-restrictive layer in someinstances. In some embodiments, other elements such as zirconium areadded to the alumina in small amounts (0.1-10%) in order to improve theflexibility, durability and toughness of the coating; for example,nanolaminate of alumina and zirconia can be applied, or a small amountof zirconia can be added as an impurity to the alumina film.

In some embodiments, this coating is applied just after the primaryadhesive sealant is used for the assembly of the IGU, but before thesecondary sealant is applied. In some embodiments, the secondary sealantis applied around the IGU before the ALD process. In furtherembodiments, a third sealant is applied over the ALD and secondarysealant after the ALD process is complete, in order to protect the ALDcoating from scratching and provide balanced coefficient of thermalexpansion (CTE) stresses on both sides of the coating.

In some embodiments, the ALD coating is deposited onto the innersurfaces of the IGU, by feeding the chemical starting materials into theIGU cavity through the gas-fill feed tubes. In one approach, the cavityis first purged with such inert gases as nitrogen by passing it throughthe first feed tube and out the second feed tube. Subsequently, ALDprecursor gas is passed into the window cavity through a first feedtube, and exhausted through a second feed tube. Nitrogen gas issimilarly applied and exhausted through these feed tubes in between eachgas exposure, in order to minimize CVD deposition. To obtain acceptablegas-restrictive properties, the film deposited this way can be as thinas 5-10 nm, in order to minimize the time required for deposition.Thicker films are also conceived, which improve the barrier propertiesand the ability of the system to maintain acceptable performance overlong-term thermal cycling. In one embodiment, the deposited film isalumina or a ceramic that is greater than 50% alumina. ALD process canbe carried out in a range of temperatures. In one approach, the ALDprocess is done at room temperature. In another approach, the ALDprocess is done at approximately 65° C. In another approach, the ALDprocess is done at 120° C.

In some embodiments, the ALD is done through a single tube, whereapplication of each precursor gas is followed by application of a vacuumto remove excess gas.

In some embodiments, the ALD film sufficiently thick to change theemissivity of the low-e coating on the inside-facing surface(s) of oneor both of the lites. In that case, it is advantageous to design a low-ecoating so that its emissivity is improved by the addition of a finalALD coat. Therefore, in some embodiments the emissivity of the interiorwindow coating will be lower after the coating process than it wasbefore the coating process.

In some embodiments, only a single exposure of precursor is required tocreate a gas-restrictive layer. Because the precursor compounds such astrimethylaluminum diffuse inside the adhesive itself during deposition,subsequent exposure to water (either in the chamber, or in the outsideenvironment) will result in a significant density of aluminananocrystals being formed within the polymer bulk. If they are ofsufficient density, these nanocrystals can be enough to create anacceptable gas-restricting layer without the formation of a true coatingon top of the adhesive. Thus, a gas-phase deposition process (whetherALD or CVD) that does not form a contiguous/continuous coating on top ofthe adhesive is explicitly envisioned here.

For IGUs, the goal of a gas restrictive coating is to keep the leak rateof argon down to 1% of the cavity volume per year, so that nosignificant change in gas composition will occur over the lifetime ofthe system.

In one embodiment of the invention, there is a desiccant incorporatedinside the IGU, and this desiccant is coated during the coating process.In some examples, the coating over the desiccant is thin enough so asnot to interfere with the performance of the desiccant. In otherexamples, the coating over the desiccant is thick enough to inactivatethe desiccant, and the desiccant must be re-activated inside the window.This can be accomplished, for example, by locally heating the desiccantwith NIR or visible or UV light, for example using a laser. This heatingprocess vaporizes residual water inside the desiccant (as even a “dry”desiccant contains some water accumulated through various handlingprocesses), which expands and breaks through the coating, thus restoringmuch of the original activity of the desiccant. Other methods of heatingthe desiccant include electrical or magnetic induction, if anappropriately susceptible material is included with the desiccant torender such an operation viable.

In some embodiments, it is desirable to deposit an ALD or other filmonly on the adhesive, and not coat other areas, such as the windowitself In such circumstances, it is preferred to use a “mask” to coverthe areas that are not intended to be coated. Thus, in one aspect ofthis invention the coating is made by a process where: (1) a maskingfilm is placed over the window glass during the coating process, (2) thebonding adhesive is coated using a coating process such as one of theexamples listed above, and (2) the film is subsequently peeled off orotherwise removed from the window. Using this approach, the window glassis not coated, but the adhesive bond is.

In another embodiment of the current invention, the multi-pane IGU uses“aerogels” to fill the internal cavity or cavities of the IGU. Aerogelsare small beads of trapped gas that in this application are placedbetween the panes of an IGU to improve its insulating value. Aerogelsfor use in IGUs have been in development for approximately 15 years andutilized in some translucent skylight applications. When using aerogels,it is challenging to coat the inside of the glass unit after applicationof the gel, because the diffusion of gas through the gel is sorestricted. As a result, when using aerogels, it is preferred to coatthe outside of the window to improve the gas impermeability of theunits.

As stated above, the methods for coating adhesive in VIGUs are similarto those for coating adhesive in IGUs, with more care given to ensurethat a coating meets the required hermeticity specification, namely,that the window maintain a pressure of less than 1 millitorr over itsdesired 20-40 year life. As a result, the details of the sealing methodswill not be recapitulated, and the methods used above may be combinedwith any approach listed here, unless specifically stated otherwise. Apreferred method for coating VIGUs adhesives is atomic layer deposition(ALD) of greater than 50% alumina at approximately 120° C. to athickness of 20-100 nm.

In the cases described below, the purpose of the coating is to extendthe lifetime of the VIGU by decreasing the rate of permeation of gasinto the VIGU cavity. In one example, the rate of diffusion of heliuminto the cavity (inclusive of diffusion through glass, bond, and metalif present) is greater than 1×10⁻⁸ cc (STP)/sec without the coating, andless than 1×10⁻⁹ cc (STP)/sec when coated. In another example, the rateof outgassing of hydrogen into the cavity is greater than 1×10⁻⁸ cc(STP)/sec without the coating, and less than 1×10⁻⁸ cc (STP)/sec whencoated.

The leak rate of gas through the coated adhesive bond will be directlyproportional to the thickness of the bond. Thus, it is generallypreferred to make the bond as thin as is manufacturable. One preferredthickness of the bond line is 75 μm, though thicknesses of 250 μm ormore are acceptable as long as the hermeticity of the coating issufficient.

In one embodiment, a VIGU may be sealed with an adhesive, and then theentire VIGU coated with a highly hermetic layer by one of theabove-mentioned methods. This approach can be used for both conventionaldouble-pane VIGUs or hybrid windows similar to the NSG Spacia 21, atriple pane window with one vacuum cavity and one air- or gas-filledcavity. A preferred method of sealing such an assembly is to prepare theadhesive-sealed VIGU, and then immediately insert the VIGU into a largearea ALD tool for coating. A typical coating is 20-100 nm of alumina,coated at 120° C.

Sealing the adhesive inside the cavity creates a requirement that theadhesive itself be non-outgassing and not react with UV light to formvolatile organic fragments; if either occurs, the pressure inside thewindow may rise above 1 millitorr as a result, degrading the window'sinsulating properties. An example of a material with excellentoutgassing properties and good UV resistance is an aerospace gradefilled or unfilled silicone, such as Dow-Corning 93-500 or NusilSCV1-2599. A secondary adhesive may be applied after the hermeticcoating to supplement the mechanical strength of the assembly andprotect the highly hermetic coating, if desired.

In some embodiments, the long-term performance of windows sealed in thisway are improved by the addition of gas and moisture getters such aszeolites; carbon dioxide sorbents such as calcium hydroxide; andreactive metals such as barium, which all act to getter gas if itoutgases from the adhesive over time. In some embodiments, the gettersare coated during the coating process. In one aspect, the coating isthin enough to not impede the flow of gas into the getter. In anotheraspect, the coating is sufficiently thick to significantly lower theactivity of the getter after the coating process. Thus, in oneembodiment, the getter is re-activated by locally heating it to releasetrapped gas and/or expand the physical area of the getter, and thuscrack the coating and restore much of the getter's original activity. Inone aspect, this heating process is done using a NIR or visible or UVlight laser. In another aspect, the getter is, or is coated onto, aconductive element, and this conductive element is heated usinginductive coupling, which firsts heat the conductive element and in turnheats the getter material. In one example, the getter is barium metal,which is coated onto a nickel wire and inserted into the window, and thenickel wire is heated by inductive coupling to approximately 700° C. orhigher to vaporize the barium. In another example, the nickel wire iscoated with lithium metal, and the wire is heated to approximately 500°C. or higher to vaporize the lithium.

The VIGU may also be prepared by bonding each lite to a metal frameusing an adhesive, and then welding the frames together in vacuum toform the final unit. By using this approach, it becomes possible to coatthe cavity-facing surface of the adhesive layer prior to welding theframes together, so that outgassing from the adhesive into the vacuumcavity is prevented. This approach thus allows a plurality of adhesivesto be used.

An example of adhesive usable by this method is Hysol 9394 two-componentepoxy. In one manifestation, the adhesive is mixed with 75 μm glassbeads and dispensed around the edge of a lite, and the lite is adheredto a metal frame made from a metal or alloy foil that is chosen to soit's CTE closely matches the CTE of the glass. The lite and frame arethen subjected to a coating process such as atomic layer deposition, sothat the adhesive bond is effectively coated by a hermetic seal. Apreferred method of creating the barrier is to first bond each lite to ametal frame, and then coat each lite individually in a large area ALDtool with 20-100 nm of alumina, coated at approximately 120° C. The twolites are brought together along with a spacer structure, and the metalfilms/foils are welded in vacuum to hermetically seal them together.Alternatively, instead of welding the lites together in vacuum, thelites are welded into a single assembly in air, and the cavity issubsequently pumped down using a pump-out tube embedded into at leastone of the lites.

In some embodiments, the adhesive surface on the outside surface of thelite is masked with tape, to prevent it from being coated. This is donein order to prevent pressure buildup inside the hermetically sealedadhesive that might lead to rupture of the coating. In some embodiments,a fillet of adhesive exposed on the outer surface of the lite, but notmasking it. This fillet will receive a hermetically sealed coating bythe aforementioned processes, but because of its greater thickness andmore extreme geometry, the coating will be very prone to fracture duringthermal cycling, again preventing pressure build-up in the adhesive. Insome embodiments, a fillet of adhesive is left exposed on the outersurface of the lite, and this fillet is physically abraded after thecoating process to remove some or all of the highly hermetic coating,achieving the same result.

In some embodiments, the inner pane of glass is masked with tape so thatthe glass is not coated. This maintains the surface properties of thewindow from previous processing, so that, for example, a low-e coatingand/or a scratch-resistant coating are not changed by the barrierapplication process. In some embodiments, the inner pane is not masked,and the previous coating systems are designed so that the coatingperformance is improved after deposition of the barrier material.

In some embodiments, the VIGU is sealed with adhesive, leaving one ortwo inlets to allow fluid communication with the cavity. The coatingprocess is then performed on the inside cavity of the VIGU, through theinlet(s), in a process described above for an IGU. A preferred coatingprocess is to deposit 20-100 nm of alumina by ALD at 120° C., where theprocess gases are introduced into and expelled from the VIGU cavitythrough the inlets. In this approach, there is no need for aconventional ALD chamber, as the cavity itself serves as the “chamber”for the reaction.

The present invention disclosed and claimed herein comprises, in anotheraspect thereof, a method for manufacturing a VIGU which uses a thinmetal seal attached to lites one and two to create the hermetic seal atthe VIGU's perimeter. One or more of the current state of the arthighly-hermetic glass-to-metal bonding methods, including ultrasonicbonding, diffusion or thermal-compression bonding, chemical bonding withor without mechanical assistance and glass-frit bonding are used to bondthe glass the metal. After the metal members are joined together tocreate a sealed VIGU, the glass to metal bond is coated on its externalsurfaces with a highly hermetic material layer. Defects and/or damage(e.g. cracking) can occur to the glass-metal seal during themanufacturing process or subsequently which do not mechanically separatethe metal to glass seals or seal area, but allow gas permeation throughthe seal. The highly hermetic coating bridges and strengthens thedefects and/or damage, prevents permeation into the evacuated cavity ofany gases, and inhibits further crack growth. A preferred process forthis aspect involves inserting the entire VIGU into a large-area ALDchamber and depositing alumina (from trimethylaluminum and water) overthe outside of the window at approximately 80° C., to a thickness of20-100 nm. The window glass itself may be optionally masked to avoidcoating with alumina. In another embodiment, the window glass is notmasked, and is subsequently coated with another material in order toimprove the transmissivity of the glass. The specific choice of materialfor this coating, as well as its thickness, depends on the thickness ofalumina used. In one embodiment, this process is used to fill and repairdefects in a glass frit-bonded VIGU made using conventional VIGUprocessing, where a thick glass frit is used to join the two lites andprovide a hermetic seal to the cavity, and no organic adhesive is used.

In another embodiment, the glass pane is coated prior to assembly usinga process such as atomic layer deposition (ALD), in order to reduce thediffusion rate of gas through the glass. In this process, a coating ofapproximately 10-100 nm is applied to the glass using ALD, in order torestrict the diffusion of helium, which can have a significantpermeability through some glass formulations. In some embodiments of theinvention, this ALD coating is greater than 50% alumina. In someembodiments of this invention, this coating drops the permeability ofthe glass to helium by an order of magnitude. Leak rate for a piece ofglass is most easily expressed in the units of cc (STP)*thickness(cm)/(s*area (cm²)), which reduces down to cm²/s, assuming a 1atmosphere pressure drop between the outside and inside of the cavity.Thus, in this example, the leak rate is taken from greater than 10⁻¹¹cm²/s to less than 10⁻¹² cm²/s for a 2 ft.×3 ft. window. This increasesthe time at which the window can maintain a vacuum of less than 1 mtorrfrom just a few years, to the greater than 10 year period needed forcommercial applications.

In another embodiment, the gas permeability of the glass for the VIGU isreduced by exposing it to a vapor containing a large alkali atom such ascesium. This may be particularly useful in applications where aborosilicate glass or fused silica is used instead of conventional sodalime glass because, for example, the CTEs of these glasses are lowerthan that of soda lime glass. These lower CTEs will result in lessmechanical stress on the edge seal when one side of the VIGU is heatedor cooled relative to the other, since the total thermalexpansion/contraction of the heated/cooled side will be less. However,borosilicate glasses possess an inherent permeability to helium that isapproximately two orders higher than that for float glass at roomtemperature. A VIGU made from a glass such as a borosilicate (e.g.,Pyrex 7740), a fused silica, or some compositions of soda lime glass maylack the required low permeability necessary to prevent helium fromdiffusing into the vacuum cavity over the VIGU's 10-40 year life, andtherefore will require a coating in order to show good long termreliability. In one example, cesium nitrate salt is disposed on or nearthe glass, and the glass is heated to greater than 400° C., above thedecomposition temperature of the cesium salt. At this temperature,cesium vapor penetrates into a small depth into the glass, and occupiesinterstitial spaces between silicon and oxygen atoms. By blocking theinterstitial spaces, the permeability of helium through the glass isgreatly reduced.

In one aspect of this invention, the process of coating the glassimproves its tolerance of compressive and tensile stresses, so that itis less likely to fracture when assembled into a VIGU. In a VIGU, thetwo lites are separated by an array of stand-off elements, especiallymetal stand-offs, which are approximately 0.2 to 1 mm each in diameter,and which bear the load of atmospheric pressure pushing in from theoutside of the lites. These metals stand-offs are pressed into the glasswith a large compressive force. If there is a small number of scratchesor other surface defects on the glass, and at least one of these defectsspatially overlaps with the stress fields created around the stand-offs,then there is a significant likelihood that the defect will propagateinto a crack, which will eventually fracture the window during its life.By coating the window with a conformal film by a process such as ALD, itis possible to fill these defects and render them less likely topropagate into a crack. Thus, in one aspect of this invention, theresistance of the glass to fracture is improved. Because this resistancedepends on the defect density on the original glass, the improvement isbest expressed as a statistical improvement in the likelihood of a pieceof glass to fracture under a given compressive load from a stand-off,where the critical load depends, in part, on the geometry of thestand-off. This improvement can be measured at the 2-sigma level,3-sigma level, 4-sigma level, 5-sigma level, or 6-sigma level, forexample. Because there are on the order of 1000 stand-offs per squaremeter of glass, it is important to have a very low critical defect leveloverall to make a successful commercial VIGU.

In another embodiment, a metal member is coated by a process such as ALDto reduce the diffusion of hydrogen out of the metal. This metal memberis then bonded to the glass using any of the aforementioned processes toform a lite, and the two lites are welded together to form a completeVIGU. One advantage of ALD is that the thickness of the deposited filmis very low, and so the welding process is not inhibited by the coating.Although the welding process described here may expose a new, uncoatedarea of metal to the vacuum cavity, the total area of uncoated metal isgreatly reduced, and thus the total rate of diffusion of hydrogen intothe cavity can be reduced sufficiently to assure the VIGU of itsnecessary commercial life. In one example, the leak rate of hydrogeninto the window cavity is dropped by an order of magnitude, for instancefrom greater than 10⁻⁸ cc (STP)/s to less than 10⁻⁹ cc (STP)/s.

In another embodiment, the glass is bonded to a metal member using anyof the above processes, and the glass and the metal are subsequentlycoated by a process such as ALD to restrict the rate of diffusion of gasinto the chamber. Such a process will reduce the diffusion into the VIGUcavity of helium through the gas, and hydrogen from the metal.

In some embodiments, a barrier coating is applied over at least oneglass surface of the VIGU, and this barrier also reduces the coefficientof friction of the glass. In a preferred embodiment, the coefficient offriction of the coating material versus stainless steel is 0.3 or lower.In one embodiment, the coating is boron nitride, as applied by atomiclayer deposition. This low coefficient of friction is especiallydesirable in VIGU configurations where one lite moves relative to theother, for example because of a difference in temperature between thetwo lites.

In some embodiments, the coating is transparent to visible light. Whilethis is not necessary if only metal or the bond line is coated, suchtransparency is useful when the window is coated. In a preferredembodiment, the transmissivity of the coated glass is greater than 85%,relative to uncoated glass. In a more preferred embodiment, thetransmissivity of the coated glass is greater than 90% relative touncoated glass. In some embodiments, this coating is aluminum oxide at athickness of 20 nm.

In some embodiments, the coating process contains more than one layer.This may be valuable, for example, to improve the resistance of the filmto cycling mechanical stresses. In one aspect, this is accomplished bypreparing a nano-laminate film using atomic layer deposition; forexample, a nanolaminate of alumina and zirconia. In another aspect, thecoating process uses a first film to provide a good gas barrier, and asecond film on top of it to provide enhanced tribological properties.For example, the first film is 20 nm of alumina as deposited through anALD process, and the second film is 50 nm of diamond-like carbon (DLC).In this case, the diamond-like carbon may not be sufficiently uniform toserve as a highly hermetic layer on its own, but is sufficiently thickto provide a low coefficient of friction.

It should be understood that the drawings and detailed descriptionherein are to be regarded in an illustrative rather than a restrictivemanner, and are not intended to be limiting to the particular forms andexamples disclosed. On the contrary, included are any furthermodifications, changes, rearrangements, substitutions, alternatives,design choices, and embodiments apparent to those of ordinary skill inthe art, without departing from the spirit and scope hereof, as definedby the following claims. Thus, it is intended that the following claimsbe interpreted to embrace all such further modifications, changes,rearrangements, substitutions, alternatives, design choices, andembodiments.

1. A vacuum insulated glass unit (VIGU), comprising: a first pane of atransparent material; a second pane of a transparent material, thesecond pane being spaced apart from the first pane to define a cavitytherebetween; at least one of a spacer and an array of stand-off membersdisposed between the first and second panes to maintain separationtherebetween; a first adhesive layer forming at least a portion of agas-tight connection between the first pane and the second pane; and ahighly hermetic coating disposed over the adhesive layer, where thecoating is an inorganic layer.
 2. A VIGU according to claim 1, whereinthe highly hermetic coating comprises greater than 50% aluminum oxide.3. A VIGU according to claim 1, wherein the highly hermetic coating hasa thickness from about 20 nm to about 100 nm.
 4. A VIGU according toclaim 1, wherein the highly hermetic coating is deposited on both acavity-facing surface and an outside-facing surface of the adhesivelayer.
 5. A VIGU according to claim 4, wherein the highly hermeticcoating on the outside-facing adhesive surface is abraded subsequent todeposition.
 6. A VIGU according to claim 5, wherein the outside-facingadhesive surface has a fillet-shaped configuration.
 7. A VIGU accordingto claim 1, wherein the highly hermetic coating is deposited on thecavity-facing adhesive surface, and not on the outside-facing adhesivesurface.
 8. A VIGU according to claim 1, wherein the leak rate into thecavity is less than 10⁻⁸ cc (STP)/sec.
 9. A VIGU according to claim 8,wherein the leak rate into the window cavity is less than 10⁻⁹ cc(STP)/sec.
 10. A vacuum insulated glass unit (VIGU), comprising: a firstpane of a transparent material; a metal member bonded to the first panewith a first adhesive layer; a second pane of a transparent material,the second pane being spaced apart from the first pane to define acavity therebetween; and a highly hermetic coating disposed over theadhesive layer, where the coating is an inorganic layer.
 11. A VIGU inaccordance with claim 10, further comprising an array of stand-offmembers disposed between the first and second panes to maintainseparation therebetween.
 12. A VIGU in accordance with claim 10, whereinthe second pane is bonded to the first metal member with a secondadhesive layer.
 13. A VIGU in accordance with claim 10, wherein thesecond pane is bonded to a second metal member with a second adhesivelayer.
 14. A VIGU in accordance with claim 13, wherein the first andsecond metal members are hermetically joined to one another.
 15. Avacuum insulated glass unit (VIGU), comprising: a first glass pane; afirst metal part bonded to the first glass pane with a first adhesivelayer; a second glass pane, the second glass pane being spaced apartfrom the first glass pane to define a cavity therebetween; an array ofstand-off members disposed in the cavity between the first and secondglass panes to maintain separation therebetween; a second metal partbonded to the second glass pane with a second adhesive layer; and afirst barrier coating on at least one of the glass panes and the metalparts, where the first barrier coating decreases the rate of permeationof gas into the cavity.
 16. A VIGU in accordance with claim 15, wherethe barrier coating is on one of the metal parts, and it reduces thepermeation rate of a specific gas into the cavity by at least one orderof magnitude relative to the uncoated part.
 17. A VIGU in accordancewith claim 16, wherein the specific gas is hydrogen.
 18. A VIGU inaccordance with claim 15, where the barrier coating is on one of theglass panes, and it reduces the permeation rate of a specific gas intothe cavity by at least one order of magnitude relative to the uncoatedglass pane.
 19. A VIGU in accordance with claim 18, wherein the specificgas is helium.
 20. A VIGU in accordance with claim 15, wherein at leastone of the glass panes supports a coating which lowers the emissivity ofglass, and where the barrier coating further lowers the emissivity afterit is applied.